There is a need in various fields to clamp plate members in place. One such field having such a need is in printing presses and more particularly rotary printing presses. For example, with conventional rotary printing presses the printing plate saddle is formed in two halves, each of which is wrapped around half of the plate cylinder. In order to mount the printing plates substrates in place a pair of locking mechanisms are generally provided on each end of the saddles. Each such locking mechanism pair would clamp the leading end of one substrate and the trailing end of the other substrate to the cylinder. Generally, the mounting of the substrates is achieved by first fixing one end of the substrate and then mounting that substrate half way around the cylinder with the other end being in a slightly slack condition when it is inserted into the clamping mechanism. The tensioning mechanism which is spring loaded would then be actuated to take up the slack and stretch the cylinder blanket and tautly mount the substrate to the cylinder. The clamping mechanism could be double ended to change the direction of rotation.